Hot water that smells like rotten eggs is often caused by a reaction inside a storage water heater, where bacteria and parts of the tank produce a sulfur gas. The smell can also come from other sources, so it is worth checking where and when you notice it.
The odor is usually unpleasant rather than an emergency. But a rotten egg smell in the air, instead of in the water, can be a sign of a gas leak, which is a very different situation.
First, Rule Out a Gas Leak
Natural gas has an added odor that many people describe as rotten eggs. If you smell it in the air near a gas water heater, stove or any other part of the home, do not try to find the source. Con Edison advises leaving right away and calling 911 or the utility once you are safe. Do not use light switches, phones or appliances while you are still inside.
A smell that only appears when hot water is running, and that comes from the water itself, points more toward the water heater or plumbing than to a gas leak.
Why a Water Heater Can Cause the Smell
Many storage tank water heaters have a metal rod inside, called an anode rod, that helps protect the tank from corrosion. In some conditions, bacteria in the water can react with this rod and create hydrogen sulfide gas, which smells like rotten eggs.
This may be more noticeable when the heater has not been used for a while, when the water temperature is set low, or after changes to the water supply. These are possible factors, not a diagnosis. The exact cause depends on the unit and how it is used.
Other Possible Sources
A quick check can help narrow things down:
- If both hot and cold water smell, the cause may be outside the water heater.
- If only one faucet smells, the drain under that sink may be the real source.
- If the smell started after plumbing work or water main work nearby, the supply may have been disturbed.
Drain odors are easy to mistake for a water smell, since you are standing over the sink while the water runs. Try filling a glass and smelling it away from the sink.
What to Avoid and When to Get Help
Do not remove parts from the water heater, raise the temperature sharply or pour chemicals into the tank. Hot water systems are under pressure, and some changes can create scald or safety risks. If you notice the smell along with leaking, odd noises or a change in hot water, mention all of it when you call.
In Bronx apartment buildings, the water heater may serve many units and be managed by building staff. Renters should report the smell to the super or landlord rather than touching the equipment.
If your hot water has a sulfur smell that will not go away, our water heater repair service can check the unit and talk through options. Call (929) 209-6183 to set up a visit.
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